Sleevelike refracting prism



Jan. 2, 1923.

C. FJENKINS. SLEEVE LIKE REFRACTING PRISM.

FILED FEB. 5, 1921.

MAM

LUihIcAM/A prism mentioned an approxi Patented Jan. 2, 1923.

UNITED STATES CHARLES FRANCIS JENKINS,

PATENT OFFICE.

OF COLUMBIA, ASSIGNOR TO A CORPORATION.

SLEEVELIKE REFBACTING PRISM.

Application filed February To all whom. it may concern:

Be it known that I, CHAnLns FRANCIS Jnxxixs. a citizen of the UnitedStates, and resident of \Vashington, in the District of Columbia. haveinvented certain new an useful Improvements in Sleevelike RefractingPrisms, of which the following is a specification, reference being hadtherein to the accompanying drawing.

Producing a circular prism of progressively varying cross section byshaping the lateral face of the peripheral zone of a plane glass disk isnot new. but while such a con struction is usable for either camera orprojecting machines for motion picture work, it has an inherent detectin that sharpness is lacking in parts of the pictures. It has been foundthat by ately cylindrical. sleeve-like glass band varied in radialthickness to produce a prism having the angle of its faces progressivelyvaried, the defect mentioned is practically eliminated.

In the accompanying drawings,

Fig. l is a perspective view of the novel prism.

Fig. :2 is a diagrammatic view showing the prism in dia'inetricalsection and connected with other parts of a motion picture machine.

In Figure 1. R represents an internally cylindrical ring having thethickness of its margins or ends gradually increasing and decreasing.from maximum and minimum,

' respectively. in passing around the curve from a certain point. Theforms of the cross sections at the lines A-B, C-D, and wy, are shownalongside those lines. The lines .\B and C-l) are slightly separated,and in this space each margin changes from maximum to minimum or viceversa. while on the opposite side of the sleeve the prism faces areparallel.

ln Figure 2. F represents a picture film, h a sprocket druln fixed'on aconstantly rotating shai't S. The prism R is mounted on a suitableholder ll in position to receive light rays from a source L thrown backb a mirror 1W1 through a diffusing. screen The prism is rotated from thedrum shaft substituting for the 5, 1921. Serial No. 442,872.

by a gear I, pinion I, shaft J, gears K. K and shaft J perpendicular tothe plane of the prism R. The light beam after passing throug 1 therotary prism to in it, is bent by a fixed prism F into the axial line ofa projection objective P0 inclined to the plane of the prism so that thebeam may pass alongside instead of through, the opposite side of theprism ring, and onward always in the fixed axial line Q; to a screen,n0tshown.

The prism here shown is here shown as arranged to make one completerevolution while the film advances a pictures width, but obviously theinvention is not limited to such embodiment.

From the construction it follows that since the prism always bends therays into the fixed path Q while one picture is passing and then quicklybegins a repetition of the cycle of movements, the picture of the screenremains in a fixed position.

It is common knowledge that in this art projecting and camera. devicesare interconvertible without invention.

What I claim is:

1. An approximately cylindrical sleevelike retracting prism having oneend ortion of its wall progressively change in radial thickness inpassing around the sleeve and also having its wall progressively changedin radial thickness in passing from said end portion toward the oppositeend portion.

2. A glass retracting prism of approximately cylindrical sleeve-likeform and having its radial thickness progressively varied, in passingaround the periphery, tochange the angle made by the prism faces.

3. A sleeve-like retracting prism having the end portions of its wallrogressively and oppositely changed in ra ial thickness in passingaround the sleeve in the same direction and also. having its wallprogressively changed in radial thickness in passing from each of saidend portions toward the opposite end portion.

In testimony whereof I hereunto signature.

CHARLES FRANCIS JENKINS.

the s ace with-

